""How could the oldest, deadliest, most divisive conflict of a proud nation come down, after decades of bitter strife, to a dispute over an insignificant fort squatting on a hunk of rock in the harbor of the South's oldest and most defiant city?"" For Klein (Unfinished Business), a professor of history at the University of Rhode Island, the key to the attempted dissolution of the Union lay in the concept of secession, as distinct from states' rights. Secession, he demonstrates in this impressive study, was not ""a fine old brandy"" reserved for special occasions but ""a house wine always on hand,"" regularly served, cheap and intoxicating. Nowhere were its effects greater than in South Carolina. Klein demolishes the myth that South Carolina was governed by cavaliers, gentlemen of honor devoted to the public welfare. Instead, he finds a state governed by a self-referencing, ingrown, money-obsessed oligarchy. Klein vividly depicts the general failure of leadership that transformed crisis into war. The government's indecisive handling of the Fort Sumter blockade began, he shows, with lame-duck President James Buchanan, whose best gifts were those of a diplomat and a lawyer. Congress was gridlocked, the party system in chaos and Abraham Lincoln was an unknown quantity whose capacities were obscured by his appearance and behavior. Lincoln's secretary of state, William Seward, believed he himself could preserve the Union without war by reducing Lincoln to a figurehead while forming a new ""national party""--two mutually reinforcing delusions, according to the author. With a novelist's skill, Klein has crafted an engrossing portrait of the nation's descent into chaos and war. Maps and photos not seen by PW. History Book Club selection. (Sept.)